1. Field of the Invention
This invention relates to a laser OLB (Outer Lead Bonding) apparatus for mounting a semiconductor device by use of laser beams and such a mounting method.
2. Description of the Related Art
FIGS. 20 and 21 each illustrate a mounting stage unit of a conventional laser OLB apparatus. The laser OLB apparatus recognizes recognition marks 4 of a substrate 3 and thus locates the substrate 3 on a stage 6. After a bonding agent 7 has been applied to this substrate 3, the laser OLB apparatus recognizes outer leads 2 and locates an IC package 1 on the substrate 3. The IC package 1 is then temporarily fixed to the substrate 3 with the bonding agent 7. Subsequently, a plurality of outer leads 2 are irradiated with laser beams 8 and bonded one by one to bonding lands. Note that irradiating positions of the laser beams are programmed beforehand in the laser OLB apparatus.
In the conventional laser OLB apparatus, however, when the IC package 1 is mounted on the substrate 3, there exist some outer leads that are buckled as in the case of an outer lead 2a shown in FIG. 20 and thereby deviate in position from the corresponding bonding lands of the substrate 3. Even in such a state, the irradiation of the laser beams is effected based on preprogrammed patterns. For this reason, there arises a problem that the operation proceeds to the next step even if ill-bonded outer leads 2 are produced. Further, there is also a possibility of forming the ill-bonded outer leads. This is derived from the following reason. Even when there is no flexure in the outer leads 2, the pitches of the outer leads 2 and of the bonding lands of the substrate 3 have some variation in terms of manufacturing processes, and yet the preprogrammed laser beam irradiation is conducted while ignoring these variations.
Further, in some cases, the outer leads 2 are bonded in a state where the IC package 1 is pressed against the substrate 3 by use of an arm and thus fixed thereto instead of temporarily fixing the IC package 1 with the bonding agent 7. In a QFP (Quad Flat Package), however, where the outer leads extend from the four sides of the package body, the following problem is induced. If the irradiation of the laser beams is performed with the IC package being pressed against on the substrate 3 by an arm 5, some leads are overshadowed by the arm 5 and thereby receive no laser beam energy. It is difficult to bond all the outer leads 2.